Portable modular video oculography system and video occulography system with head position sensor and video occulography system with animated eye display

ABSTRACT

A goggle based light-weight VOG system includes at least one digital camera connected to and powered by a laptop computer through a firewire connection and allows for region of interest image processing. The VOG system is a modular design whereby the same goggle frame or base is used to build a variety of digital camera VOG systems. The VOG system may track and record head position and goggle slippage. An animated eye display may provide data in a more meaningful fashion. An EOG system may be incorporated directly into a goggle base. The digital camera may digitally center the pupil in both the X and Y directions. A calibration mechanism may be incorporated onto the goggle base. The VOG system may be a modular design whereby the same goggle frame or base is used to build a variety of digital camera VOG systems.

RELATED APPLICATIONS

This application is a divisional application of pending U.S. patentapplication Ser. No. 10/704,529 filed Nov. 7, 2003 entitled PortableVideo Oculography System and which published May 12, 2005 as publicationnumber 2005-0099601, which publication is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to clinical eye tracking systems, and moreparticularly to a self-contained, portable, high speed, videooculography modular goggle based system, and a video oculography systemwith a head position sensor and a video oculography with an animated eyedisplay.

2. Background Information

Accurate eye position recording and monitoring in three dimensions(3D-yaw, pitch and torsion rotation about line of sight) is asignificant clinical diagnostic tool in the field of vestibulardisorders such as vertigo and other neurological disorders. Anon-invasive technique for recording eye position relative to the headis to use a camera to record eye position relative to the head, known asvideo oculography or VOG. VOG systems are used by VestibularResearchers, Ophthalmologist, Otolaryngologists, Physical Therapists,Neurologists, Audiologists, Balance Clinicians, Neurophysiologists,Physiologists, Neuroscientists, Occupational Therapists, and others.

Image processing software is utilized to interpret the images to provideobjective data of eye position. This type of image processing softwareis described in “A GEOMETRIC BASIS FOR MEASUREMENT OF THREE-DIMENSIONALEYE POSITION USING IMAGE PROCESSING” Vision Res. Volume 36. No. 3, Mooreet al., pp 445-459, 1996, which is incorporated herein by reference.

The existing VOG systems can be categorized as either earth mounted orhead mounted systems. The oldest method uses earth fixed cameras andattempt to limit movement of the head. The relative movement of the headand the camera would be interpreted as eye movement. These systemsattempt to stabilize or immobilize the head with head holders, headrests, chin rests, or bite bars. Although archaic, this type of systemis still used extensively in some laboratories and many clinicalenvironments. The biggest disadvantage of these systems is the inabilityto remove all head movement. Even the smallest head movements (e.g.resulting from breathing, talking, involuntary postural modification,and from fatigue etc.) cause significant inaccuracy in the measured eyemovement. These systems are particularly unsuitable when inertialstimuli (e.g. a rotational chair) are delivered to a subject in order toproduce vestibular responses, since these stimuli also tend to generatehead movement. This equipment is often heavy and bulky since it must bestrong enough to support and attempt to restrain the head of a subject.

Another classification of earth mounted VOG systems are systems thatattempt to measure eye movement using a space fixed (earth mounted)camera without a head holder mechanism. In general, these systemsattempt to deal with head movement by first tracking the head and thenthe eye within the head. In practice, a subject must actively suppresstheir head movements to within a small range of translations in order tostay within view of the camera. Further, rotations of the head are quitedifficult to detect using image processing and so these systems sufferfrom an inability to distinguish between a change of eye position in thehead or a change of head position during maintained gaze. These systemsmust also use a wide-angle lens in order to digitize an image thatincludes the head movements. Consequently, little picture resolution isavailable for the analysis of the eye position. As a result of theselimitations, these systems are generally only able to measure horizontaland vertical changes in relative eye/head position

Another earth mounted VOG system attempts to measure the eye position byfirst tracking the position of the head and then moving a camera ormirrors to get an image of the eye with higher magnification andresolution. These systems also share many of the disadvantages of theother VOG earth fixed camera systems including the inability toaccurately distinguish between head translation and rotation. Further,the mechanisms used can be complicated expensive noisy and distracting.

A second classification of VOG systems is the head mounted system. Inone type of head mounted VOG system, head mounted cameras are supportedby an adjustable headband often modified from the helmet insert takenfrom a mining or welding helmet. The cameras may be mounted above theeyes and are directed down towards hot mirrors that reflect an infraredimage of the eye. Head mounted eye movement recording systems are lessprone to the errors from head movement, because the cameras move withhead. Further this method for attaching the cameras to the head isparticularly popular because the headsets can be easily fitted to anysubject without modification. The camera mounting position above theeyes also seems fairly natural because hardware tends to stick up intothe air. This placement keeps the centre of gravity closer to the headand reduces the inertial lag on yaw head movements. Despite theseadvantages, all head mounted video eye movement measurement systemsobviously suffer from the need to wear equipment and be connected, vialeads, to the analysis hardware. Further, the headband can be painful ifit is tightened enough to effectively suppress slippage of the headsetduring head movement.

The camera may also be mounted to the side of the headband head mountedVOG systems. The main advantage of mounting cameras to the side ratherthan above the eyes is that the centre of mass of the headset tend to befurther back towards the head and so these headsets don't tends to pitchthe subject's head forward as much as some other arrangements. Thiscamera position also can provide better power supply and data outputaccess (i.e. the electrical and control feeds). The main disadvantage ofthis mounting position is that the headsets tend to become quite wide.These headsets tend to move relative to the head during the yaw headmovements that are common during vestibular testing.

The camera may also be mounted in front of headband in the headband headmounted VOG systems. The main advantage from mounting cameras towardsthe front of the subject is that no hot mirrors are required to reflectan image of the eye into the cameras. This lack of hot mirrorssimplifies the construction and adjustment of the headsets and mayimprove the quality of video images. However, while front mountedcameras might suit light occluded systems where darkness prevents thesubject from seeing them, they don't suit most video headsets that useheadbands because these may not have an open field of view. Apart fromthe obstruction to vision, cameras in front of the subject can providevisual suppression and orientation cues that may affect their eyemovement responses. The headsets with front mounted cameras also tend tohave a centre of gravity that is further away from the head.

In place of the headband, some head mounted VOG systems utilize goggles,similar to those on diving masks, in order to attach cameras to thesubjects face. These headsets benefit from a silicon skirt that conformsto the face and stabilizes the cameras. Goggles also leave the headclear for the use of other devices that may be utilized in variousclinical applications. Another advantage of goggles is that they arewell suited for the construction of light occluding headsets as well asthose with an open field of view, or those that are convertible betweenthe two. The disadvantage of goggles style head mounted VOG systems isthat they can be uncomfortable if the cameras and other hardware is tooheavy and weighs down on the subject's head.

Some research head mounted VOG systems use video cameras mounted on theheadset with individually molded plastic or fiberglass masks. Thesemasks are particularly stable and good at suppressing relative cameraand head movement. Molded masks also tend to spread the weight of thevideo headset over a large surface area and do not produce the pressurepoints characteristic of some other methods. However, individuallymolded masks can be time-consuming and costly to make and are thereforenot convenient for the clinical testing of large numbers of patients.Hybrid masks that combine a headband and standard molded mask section donot have these disadvantages but do not seem to benefit from theadvantages either.

Another head mounted VOG system utilizes a helmet for camera mounting.The helmet style video headset benefits from a more even distribution ofweight over the top of the head and from the balance provided by moreweight towards the back. Helmet style video headsets are heavier thanmany other systems and so they tend to shift around during vigorous headmovement. They are also quite bulky and prevent the application of headholders.

Another head mounted VOG system utilizes standard glasses construction(i.e. spectacle) for camera mounting. The advantages of spectacle typevideo headsets include that they can be very small and light, and areeasily transportable. The disadvantages of this method include thediscomfort from heavy equipment resting on the bridge of the nose. Withvery small contact area, spectacles can also be prone to movementrelative to the head in response to inertial forces.

There remains a need for truly portable VOG systems. Further, therecontinues to be a need for accurate meaningful output for the cliniciansin VOG systems without significant discomfort to the patients.

The above discussion concentrates on the deficiencies in the mechanicaldesign of existing VOG systems. In addition to those issues, existingVOG systems are designed as one-of-a kind testing structures. Thisapproach leads to expensive end products. Existing VOG systems alsosuffer from poor camera design, camera power supply issues, and datatransfer problems.

Analog cameras in existing VOG systems provide data regarding eyeposition for analysis as is known in the art. During testing the visualimage of the eye(s) is often displayed in real time as a method for theclinician to follow and interpret the data. In other words a real videoimage of the patient is displayed with a graphed display of the data(e.g. a chart of eye vertical and horizontal position change over time).These may also be recorded for later review. The realistic eye image ofthe video does not always easily illustrate eye movement.

Clinicians have stated that existing VOG systems on the market sufferfrom the following drawbacks: the excessive weight of goggles, theycan't be used with droopy eyelids; difficulty with set-up; effectivetorsion measurements of the eyes are not available; lack of the sensorfor head positioning; difficulty in viewing eyes; limited in the numberof targets presentable to the patient; low sampling rates; softwarelimitations and inflexibility; no ability to focus the camera; andconcerns over image resolution.

There is a need to address at least some of these problems as well andstill provide a portable, affordable VOG system providing accuratemeaningful output for the clinicians in VOG systems.

SUMMARY OF THE INVENTION

In accordance with one non-limiting embodiment of the present inventiona video oculography (VOG) system comprises a light-weight head mountedbase adapted to be attached to a patient's head, at least one digitalcamera removably attached to the base and a controller coupled to the atleast one camera, and wherein the VOG system of the present invention isa modular design in that the same goggle frame or base is used to buildmonocular front mounted digital camera VOG systems, binocular frontmounted digital camera VOG systems, monocular side or top mounteddigital camera VOG systems, binocular side or top mounted digital cameraVOG systems, etc

The VOG system according to the present invention may utilize region ofinterest image processing. The VOG system of the present invention isdesigned to track and record 3-D movement of the eye (generally movementin an X-Y plane and eye rotation or torsion about the line of sight)generally as found in some of the prior art systems, however the presentdigital based system is designed to further track pupil dilation,providing the clinician with further critical data for diagnostictesting. The pupil size can be calculated as a byproduct of pupil centercalculation using existing pupil center locating technology.

The controller may provide power and control signals to each camera andreceive and storing data signals there from, and may include a laserattached to the base, wherein the laser is visible to the clinicianwhile the patient is wearing the head mounted base. The laser isdirected away from the base and is configured to be utilized tocalibrate the system.

The portable VOG/EOG system according to the present invention may be agoggle head mounted system with at least one digital camera of at least30 hz generally connected to and powered by a computer through afirewire connection. The computer may be a laptop portable computer(generally less than about 3 kilograms), whereby the entire system willbe less than 8 kilograms and preferably less than 5 kilograms, and mostpreferably less than 4 kilograms. The weight of the goggles may becritical in that the lightweight goggles have lower inertia and moveless improving accuracy of the system. The low inertia goggles of thepresent invention provide a 3d system and weigh less than 500 grams,preferably less than 300 grams and most preferably less than 200 grams.

The digital camera will allow for digital centering of the patient'spupil at least in one direction through concentrating on the region ofinterest, and preferably, in two directions (X and Y). The use ofdigital centering eliminates the need for a mechanical adjustmentmechanism (e.g. a slide) in the given direction. Using digital centeringfor both the X and Y (yaw and pitch) directions eliminates any grossadjustment in those directions.

The VOG/EOG system according to the present invention incorporates ahead fixed calibration mechanism in the form of an integrated laserpointer on the goggle base or camera housing. The calibration mechanismis incorporated directly into the goggle base and powered from the samesource powering the digital cameras. This construction greatlysimplifies and quickens the calibration steps and improves accuracythereof.

The VOG system of the present invention may further include a headtracking sensor to track and record a patient's head position. The headposition data may be used to supplement other data and possibly toassist in calculating any goggle slip that occurs. Essentially byknowing the goggle mass and inertia values relative to the patient andthe head movement data through a head position sensor an algorithm maybe developed to approximate the goggle position/slippage (e.g.approximating the static and kinetic friction between the skirt of thegoggle and the patient and the force applied by the goggle strap anappropriate algorithm may be developed). Calculated goggle slip can thenbe removed from the eye movement data through appropriate software.

The VOG system of the present invention is designed to provide ananimated eye display with variable, clinician controlled gain to theclinician to provide data in a more meaningful fashion. Specifically,subtle movements are more easily visualized. The animated eye can moreeasily convey position and can include a scaling factor, or gain, tosupplement the illustrated animated eyes. The animation may includevisible indicia, e.g. cross hairs at the pupil center in front view. Inplan view an animated eye may include a line of sight to visiblyillustrate where a given eye is focused on.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the” include plural referents unlessexpressly and unequivocally limited to one referent. The features thatcharacterize the present invention are pointed out with particularity inthe claims which are part of this disclosure. These and other featuresof the invention, its operating advantages and the specific objectsobtained by its use will be more fully understood from the followingdetailed description and the operating examples.

These and other advantages are described in the brief description of thepreferred embodiments in which like reference numeral represent likeelements throughout.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1-3 are perspective views of a goggle for the goggle based VOGaccording to the present invention;

FIG. 4 is a schematic sectional side view of the goggle illustrated inFIGS. 1-3;

FIGS. 5 a and b are schematic sectional side views of alternateadjustment mechanisms for a camera used in the goggle of FIGS. 1-3;

FIG. 6 is a front view of an eye tracking camera assembly for use in theVOG system according to the present invention;

FIG. 7 is a schematic view of a top camera mounted non occludedbinocular VOG system according to the present invention;

FIG. 8 is a schematic view of a top camera mounted monocular goggle fora VOG system according to the present invention; and

FIG. 9 is a view of one type of display available to the clinician inthe VOG system according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-4 illustrate a goggle headset for an integrated videooculography and electro-oculography (VOG/EOG) system 10 according to thepresent invention. The system 10 is a goggle based system using a goggleframe or base 12 for fitting onto the patient. The base 12 isessentially a frame for swimming or diving goggles such as manufacturedby Technisub S.p.A., and described in U.S. Pat. No. 5,915,541, which isincorporated herein by reference. The base 12 provides a skirt fordistributing the forces around the face and which conforms to the face,and which can be critical for occluded VOG systems. The occluded systemssimply refer to systems where external light is blocked out for at leastone eye. The base 12 is far more universal than an individual faceformed mask.

Each eye portion of the base 12 includes a mounting member 14. Themounting members 14 are used for constructing any of a variety of frontmounted VOG systems in accordance with the present invention. One member14 may be left open to provide a field of view of at least 30 degreeshorizontal and 30 degrees vertical. Alternatively one member 14 may becovered with a cap 15 to provide an occluded monocular system. Anotherembodiment could provide one or two caps 15 each with an optical frenzellens, wherein the clinician can view the patient's eye through frenzellens. In the VOG/EOG system shown in FIGS. 1-4 one member 14 receives adigital camera unit 16. Both members 14 could receive a digital cameraunit 16 forming an occluded binocular front mounted VOG system accordingto the present invention.

The digital camera unit 16 includes a digital camera operating at leastat 30 hz (30 frames per second), although 120 hz-200 hz cameras and evenhigher are available. Another aspect of the present invention is theconcept of utilizing the same camera 16 and increasing the operatingcycles by trading off the total resolution. As a representative example,if the pupil location were simulated with ten, five or even points (i.e.a very low resolution image of the eye) than the speed with the samecamera can be drastically increased. Such limited resolution would beimpractical for most diagnostic applications, but may be suitable for asports training application (e.g. baseball batters or golf players).Suitable cameras for the unit 16 are sold under the name iBot camera,StealthFire camera, Firefly II, and Scorpion camera, as a representativesample. Some of these cameras are sold through Point Grey and can befound at http:/www.ptgrey.com/. These cameras typically operate on aregulated 3.3V DC and have a resolution of at least 640×480 althoughhigher resolutions cameras such as 1024×640 are also currentlyavailable. A 480×320 resolution image (or less) is available and may besufficient particularly where one desires a higher transmission rate.

As shown in greater detail in FIGS. 4 and 5 a and b, the camera units 16include an outside mounted Z axis adjustment mechanism 18. Theadjustment mechanism 18 allows for the focus to be adjusted for thecamera unit 16 while the goggle base 12 is on the patient (e.g. fromoutside of the goggle base 12) without allowing light to enter. Theadjustment mechanism 18 is effectively a slide mounting for the cameralens with an adjusting screw for the displacement of the slide in FIG. 5a. Alternatively the mechanism 18 may be a stepper motor, such as in acomputer hard drive, as shown in FIG. 5 b.

Regarding the centering of the camera in the camera unit 16 onto thepupil, the use of high resolution digital cameras allows this to beaccomplished digitally. Specifically when the pupil location isidentified, such as by using the algorithm described in the “A GEOMETRICBASIS FOR MEASUREMENT OF THREE-DIMENSIONAL EYE POSITION USING IMAGEPROCESSING” article discussed above, the software will crop the image tothe region of interest. In other words, the system will ignore the data(after the centering) outside of the relevant portion of the digitalimage (i.e. the region of interest that may be a 460×335 pixel image)centered on the pupil. In this manner the software will avoid the needfor mechanical centering devices, thereby decreasing weight andincreasing system efficiency. Further some cameras may be able to onlyselect a given region of interest in which the data of the unusedportions need not be transmitted, thereby either increasing the speed ofthe transmission or increasing the resolution of the region of interestwhereby the region of interest will be a 640×480 (or 1024×640 or 480×320or less as desired) pixel image of the region of interest. Theelimination of mechanical centering devices with one of the optionsabove is referred to as digital centering within the meaning of thisapplication. The high resolution digital cameras of the VOG system 10allows the system to track and record 3-D movement of the eye (generallymovement in an X-Y plane and rotational movement) and to further trackpupil dilation, providing the clinician with further critical data fordiagnostic testing.

The camera unit 16 also shows a location for a laser 20 which can act asa calibration system for the goggles while on the patient's head. Thelaser 20 will point away from the camera base or goggle base 12 and willbe utilized to calibrate the system 10 such as on a wall a specificdistance away. The laser 20 can also be used to monitor and control headmovement. For example, the clinician may instruct the patient tomaintain the visible laser image of the laser 20 on a specific point ormove this image along a desired path, while the clinician can watch forvariation of the laser image position from the desired location ordesired path. Generally, the cap 15 will be removed and the patientasked to focus his eye on the laser image (e.g. a cross hair, or otherimage) on a surface a known distance away. The laser 20 is fixedrelative to the head and thereby automatically eliminates head movementin this calibration step. In an occluded system the patient may not seethe image of the laser 20, but the clinician can still monitor movement,and the patient need not see the laser image to move his headhorizontally, vertically or maintain no movement of his head. Theintegrated laser 20 is a significant tool for the clinician.

The camera unit 16 may further include a pair of infrared LEDs 22 and apair of visible light LED's 24 facing the patient. The infrared LEDs 22allow the camera to obtain images in an occluded environment and thevisible LEDs 24 allow visual stimulus to be supplied to the patient inan occluded system. The LEDs 22 and 24 can be changed in number,position, color as desired by the clinician, and can be controlled bythe operator. In other words the system 10 can be easily designed toaccommodate any lighting arrangement with LED's as the cliniciansindicate is desirable. As an alternative, a fiber optic light can be runin front of the camera lens, to the center of the camera lens anddirected at the patient whereby the patients focus on the light willalso be centered on the camera. A single fiber optic strand issufficiently thin to avoid interference with the camera image.

A key aspect to forming a portable VOG system according to the presentinvention is the data, the power and the control coupling for the cameraunit 16. The VOG system 10 utilizes an IEEE 1394 cable, also called afirewire cable 28, for each camera unit 16. The firewire carries twotwisted pair of signal wires used for data transmission and a twistedpair of power cables used for power supply. Through the use of digitalcameras, low power LED elements 22 and 24 and laser 20, a 5V powersupply will be sufficient. Such a power supply can be obtained from astandard laptop computer such as computer 30 shown in FIG. 7.

The digital camera uses a conventional voltage regulator to step downthe input voltage to 3.3 V DC. A typical firewire uses a 6-pinconnection which is found on most Macintosh® Laptops, IBM® or compatibledesktops and Macintosh® desktops allowing direct connection thereto.Some laptops do not have a 6 pin connection and only have a 4 pincommunication link only port. A specialized adaptor can be made using astandard fire-wire adaptor (connects the four communication lines)together with a set of leads to a USB port for power. Othermodifications to accommodate this arrangement may be made (e.g. replacethe lead on the camera, or use an adapter, such that it can plug intothe iLINK port on a SONY® VAIO which will free up the PCMCIA and USBports for other uses).

The system 10 provides a completely portable system 10 since thecomputer 30 may be a laptop portable computer 30. A conventional laptopcomputer 30 weighs generally less than about 3 kilograms, and thegoggles will generally weigh less than 1 kilogram (and preferably lessthan 300 grams and most preferably 200 grams) whereby the entire systemwill be much less than 8 kilograms and generally less than 5 kilograms(with current laptops the system may be about 4 kilograms). The computer10 may also be replaced with a smaller device such as a sub-notebook(not shown), which is used merely for data acquisition and control ofthe components (rather than analyzing and displaying the data). With theuse of a smaller device the weight of the system drops even further toabout 2 kilograms or less. This system would allow tests to be performedessentially anywhere and the data later transferred to a separatecomputer (even a desktop) for analysis and display. A portable systemwould be those less than about 10 kilograms, since heavier than thatthey will become cumbersome and unwieldy for the clinician. The system10 is of such light weight that the system can be carried by a patient,such as on a rotational chair.

As discussed above the digital camera of the unit 16 will allow fordigital centering of the patient's pupil at least in one direction. Theuse of digital centering eliminates the need for a mechanical adjustmentmechanism (e.g. a slide) in the given direction. Using digital centeringfor both the X and Y directions eliminates any gross adjustment in thosedirections.

The VOG system according to the present invention further incorporatesan EOG system that can operate independent of, or preferably inconjunction with, the VOG system to supplement the acquired data. TheEOG system is incorporated directly into the goggle base 12 and poweredfrom the same source powering the digital cameras 16. Specifically thegoggle frame 12, and the skirt thereof in particular, provide easymounting locations for the sensors needed for conventional EOG system.The sensors can provide eye location when a patients eyes are closed,which, of course, the VOG system cannot. The firewire 28 allows for thedata of the integrated EOG system to be sent to the computer 30. Thisdata can be used to correct the eye position data of the VOG system andsupplement such data when the patient's eyes are closed. An integratedEOG/VOG system 10 will thereby provide greater accuracy in the dataresults and provide further testing options to a clinician in a singledevice. For example, one conventional diagnostic test is to examine eyeposition with eye closure, and the EOG/VOG system 10 allows this test tobe easily accomplished with other VOG tests. The sensors can be used toconvey any physiologic data to the clinician, including but not limitedto EOG data. In addition to or in place of the EOG related data theclinician may desire the sensors to convey patient temperature, bloodflow data, blood pressure data, patient perspiration data, patient heartrate data, goggle position or slippage data, head position data(discussed above), light sensor (occluded systems) or any physiologicdata that may be desired.

The VOG system 10 of may further include a head tracking sensor (notshown) attached to the base 12 to track and record a patient's headposition. Precise position sensors are known in the art such as aninertial measurement unit from Inertial Sciences, Inc. The head positiondata may be used to supplement other data and possibly to assist incalculating any goggle slip that occurs, wherein knowing the goggle massand inertia values relative to the patient and the head movement datathrough a head position sensor an algorithm may be developed toapproximate the goggle position/slippage. Essentially the algorithm mayapproximate the static and kinetic friction between the skirt of thegoggle base 12 and the patient and the force applied by the goggle strapand use the head position data to calculate the acceleration of thepatients head and thereby approximate the goggle slippage. Calculatedgoggle slip can then be removed from the eye movement data throughappropriate software. Another head tracking method is through use of aseparate camera for recording and tracking such movement. Thisadditional system requires a separate imaging processing for the headmovement.

The VOG system 10 provides an animated eye display such as shown in FIG.9 to the clinician to provide data in a more meaningful fashion. Thedetails of animating an eye from given data can be found at thefollowing website:http://user.cs.tu-berlin.de/˜fidodido/StdArbeit/stdarbeit.html whichshows eye animation for data playback and is incorporated herein byreference. The animated eyes 40 can more easily convey position and caninclude an adjustable scaling factor, or gain 42, to supplement theillustrated animated eyes. The gain is for X, Y and rotational ortorsional movement (with rotation being the most difficult to accuratelymeasure). The controllable gain 42 may be separated into the specificcomponents if desired. The animation may include visible indicia, suchas cross hairs 44, at the pupil center in front view to assist inviewing movement, in particular rotational movement. Additionally avisible line of sight can be provided in a top view. The digital imageand analysis thereof for pupil center provide all the real time dataneeded to construct and move the animated eyes 40. The eyes 40 may alsobe displayed with graphical data 46.

The VOG system 10 of the present invention is intended to be a modulardesign. There are other high priced convertible systems such as anoccluded/open face/monocular/binocular as can be found at websitehttp://www.smi.de/3d/index.htm. However the system 10 of the presentinvention is modular in that the same goggle frame 12 or base is used tobuild occluded monocular front mounted digital camera VOG system 10 asshown in FIGS. 1-4, or binocular front mounted digital camera VOGsystems, or a monocular top mounted digital camera VOG system 10 asshown in FIG. 8 (in which unit 16 is replaced with a side mounted unit16′ and a hot mirror 50 for reflecting the image into the camera), orbinocular top mounted digital camera VOG system 10 as shown in FIG. 7(with units 16′, hot mirrors 50 and center mounted calibration laser20′), or frenzel goggles with caps 15 having lenses therein, or avariety of other systems through mixing of these components and addingother modular components.

As shown in FIGS. 7 and 8 the same mounting member 14′ can be used fortop mounted cameras 16′ and for side mounted cameras wherein themounting position of the camera and the hot mirrors would be switched.The key feature is that a wide variety of systems can be built on asingle platform, the goggle frame 12. The clinician can build numeroussystems through selective combinations of mounts and cameras.

Various modifications of the present invention may be made withoutdeparting from the spirit and scope thereof. For example, the system mayinclude a digitized objective view of the lid position to provide anobjective analysis for ptosis. The described embodiment is not intendedto be restrictive of the present invention. The scope of the presentinvention is intended to be defined by the appended claims andequivalents thereto.

1. A modular, portable video oculography system comprising: a headmounted base adapted to be attached to a patient's head; a plurality ofcameras selectively, removably attached to the base, each cameraconfigured to take images of one of the patient's eyes, and wherein atleast one camera is configured to be mounted in a different orientationrelative to the patient's eye than at least one other camera which isconfigured for mounting relative to that patient's eye; and a controllercoupled to each camera which is coupled to the base and receiving andstoring data signals there from.
 2. The system of claim 1 wherein thecameras selectively provide for top mounted cameras for each eye andside mounted cameras for each eye.
 3. The system of claim 2 wherein atleast one of the cameras forms an occluded environment around thepatient's eye when attached to the base and is configured for operationas an occluded video occulograghy camera.
 4. The system of claim 3wherein at least one of the cameras forms a non-occluded environmentaround the patient's eye when attached to the base and is configured foroperation as an occluded video occulograghy camera.
 5. The system ofclaim 1 wherein at least one of the cameras is configured for operationas a non-occluded video occulograghy camera.
 6. The system of claim 1further including frenzel lenses selectively, removably attached to thebase, each frenzel lens allowing a user to inspect the patient's eyethrough the lens.
 7. The system of claim 1 wherein the controller isused to track and record movement of the eye in an X-Y plane, androtational movement of the eye and wherein the controller displays ananimated image of the patients' eye.
 8. The system of claim 1 furtherincluding head tracking sensor mounted to the base.
 10. A videooculography system comprising: a head mounted base adapted to beattached to a patient's head; at least one digital camera attached tothe base; head tracking sensor mounted to the base; and a controllercoupled to each digital camera and to the head tracking sensor andreceiving and storing data signals there from.
 11. The system of claim10 wherein the controller is used to track and record movement of theeye in an X-Y plane, and rotational movement of the eye and pupildilation of the eye.
 12. The system of claim 10 wherein the controllerconfigured to crop the images to a defined region of interest of eachimage, whereby the controller is configured to ignore the data outsideof the region of interest of the digital image following the cropping.13. The system of claim 10 wherein each camera is a digital cameraoperating at least at 30 frames per second.
 14. The system of claim 10wherein controller utilizes the head tracking sensor to calculate goggleslippage.
 15. The system of claim 10 wherein the controller displays ananimated image of the patients' eye.
 16. The system of claim 10 furtherincluding an array of light elements on the goggle base directed at thepatients eye.
 17. The system of claim 16 wherein the array of lightelements is an annular array and includes at least a pair of infraredLED elements and at least a pair of visible light LED elements facingthe patient.
 18. The system of claim 10 wherein a plurality of camerasare removably attached to the base.
 19. A video oculography systemcomprising: a head mounted goggle base adapted to be attached to apatient's head; at least one digital camera attached to the base; and acontroller coupled to each digital camera and receiving and storing datasignals there from, wherein the controller displays an animated image ofthe patients' eye.
 20. The system of claim 19 wherein the controller isused to track and record movement of the eye in an X-Y plane, androtational movement of the eye and pupil dilation of the eye and headtracking sensor mounted to the base.